The National Women's Hockey League is laying the groundwork for adding two expansion franchises for the 2018-19 season, a league source told Sporting News.

Sporting News also learned league executives held meetings with at least four markets during the offseason, some of which have included on-site visits. During a media conference call Monday, NWHL commissioner Dani Rylan alluded to a summer filled with travel as she prepared for the 2017-18 season.

In February, the NWHL issued a press release about the shortened 2016-17 season that included an update about possible expansion. The league made it clear that expansion wouldn't come until the 2018-19 season, at the earliest.

From that press release:

“We have received interest from several markets and prospective ownership groups, and we will review these options over the next year,” Rylan said. “We’re grateful for their enthusiasm for the NWHL and professional women’s hockey. Women's hockey is one of the fastest growing sports in North America. Last year alone, USA Hockey saw close to 5 percent growth in girls' registration. It's only a matter of time before we'll have to expand to accommodate both the talent pool and the fan base.”

At the time, not much was made of Rylan's comments about expansion opportunities. But it now appears that adding new franchises has been a top priority of Rylan's for quite some time.

So, which markets are Rylan and the NWHL's other executives looking into? There are some breadcrumbs we can follow that point to at least two strong candidates.

The NWHL is scheduled to play two regular season games in neutral cities this season: Rochester and Pittsburgh. The Pittsburgh Penguins and the NWHL collaborated for the 2017 NWHL All-Star Weekend. It appears that the experience was positive for both parties .

On Monday, Rylan confirmed she has been exploring options to collaborate with NHL teams.

Rylan also confirmed Monday that the 2017 All-Star Weekend will be held at a neutral site. One potential landing spot is the nation's capital. The commissioner told the media that there's interest in that market.

"We saw great success bringing our All-Star Game out of market last season," Rylan said. "And [Washington, D.C.] is definitely on our short list of cities that we believe would host a game or even an expansion franchise."

Both Pittsburgh and Washington are home to NHL teams and are proven hockey markets. They are also within striking distance of bus travel for the league's founding four franchises. Thus far, the NWHL has relied on buses to shuttle teams around the East Coast. It's because of this that it's unlikely we'll see expansion teams in other hockey hotbeds like Minnesota or Michigan.

If Rylan can add two more teams to the fold by the 2018-19 season, it would be a massive victory for both the league and the sport as a whole. Women's hockey has proven to be one of the most popular sports of the Winter Olympics. And this year the spotlight for North American fans will be even more focused on the women's game with NHL players not traveling to PyeongChang.

The popularity of women's hockey in America may be as high as it's ever been. The United States women's national team's "Be Bold for Change" campaign before the 2017 Women's World Championship received coverage on major networks. There are more hockey fans who know the names of NWHL and national team stars than there were a year ago.

Adding to that momentum is the NWHL's new partnership with Twitter. The social media platform will live stream 19 games this season, including two preseason games and the 2018 NWHL All-Star Game. The partnership will bring NWHL hockey to hockey fans across the globe, regardless of whether or not they have a Twitter account.

All signs point to this being the right time for the NWHL to start planning expansion. The big question now is where the money is going to come from. There's a chance that it could come as a result of partnerships with NHL franchises, especially with Pittsburgh and Washington, D.C., looking like the most likely sites for expansion.

It will be a story worth keeping an eye on as the NWHL prepares for its third season.